The present invention relates to electric plug and socket assemblies and more particularly to substantially self-sealing electrical plug and socket assemblies for heavy-duty truck tractors.
Heavy duty trucks are composed of a tractor and one or more trailers coupled in series to the rear portion of the tractor. The trailers are equipped with various electrical devices which are powered from the tractor. To establish an electrical connection between the tractor and the trailer, an electrical cable is connected between the back of the tractor and the front of the trailer. Similar connections are also made between trailers if the truck rig includes a plurality of trailers.
The electrical cable has, at each end, suitable plugs configured to connect to cooperating sockets mounted, respectively, in the rear wall of the tractor cab and the front end of the trailer. The basic geometries of the electric cable plugs and the cooperating structures of the sockets are the subject of applicable SAE (Society of Automotive Engineers) standards, specifically SAE standard J560. Standardizing the geometries of the sockets and plugs ensures that any trailer can be electrically connected to any tractor using any cable assembly. SAE standard J560 is incorporated hereinto by reference.
Popular cable end plug and socket arrangements are described in catalog pages 12, 15 and 16 of the current catalog (CAT100) published by Phillips Industries, 12070 Burke Street, Santa Fe Springs, Calif. 90670, which is incorporated herein by reference. According to those arrangements, the socket is adapted to mate with the plug. The plug can be molded onto the end of a seven-conductor electrical cable; see for example, Phillips Part Nos. 16-7401 and 16-7402 (catalog page 16) in which such plugs are shown mated to sockets 16-726 and 16-826, respectively. The individual conductors in that cable connect within the molded plug body to female terminals which are disposed in an array corresponding to the array of male terminals which extend from the rear of socket. The female terminals are accessible at an end wall of a cavity bounded on its sides by a sleeve which is configured internally to mate intimately with the exterior of the barrel-like rear portion of the socket. The rear portion of the socket defines a linear key portion which cooperates in a keyway formed in the sleeve to assure that the plug and the socket have the correct angular relation to each other when they are mated together. The socket has an apertured spring blade cantilevered from the rear face of a socket mounting flange; the aperture in that spring blade receives a projection on the exterior of the plug sleeve when the plug and socket are mated, thereby holding the plug and the socket in that mated engagement. The projection with which the spring blade cooperates preferably is the exterior of the sleeve keyway.
The socket includes a flange which surrounds the socket barrel at its forward end and lies in a plane normal to the length of the barrel. A pair of mounting holes are formed through that flange adjacent respective sides of the socket barrel. Those mounting holes are used to mount the socket to the exterior surface of the rear wall of a truck tractor. The tractor rear wall has formed through it a corresponding pair of holes located on either side of a central larger hole which is sized to receive the barrel of the socket. A gasket, having holes through it in the same pattern as the holes in the tractor wall, also is used to mount the socket to the tractor; the gasket is interposed between the tractor wall and the socket flange, and a pair of nuts and bolts are used in the mounting holes to clamp the gasket socket to the tractor wall. The plug is then mated to the socket barrel on the other side of the tractor wall.
The socket body, including its mounting flange, is made of a hard material, such as die cast metal or glass filled molded nylon. The body of the plug, on the other hand, is molded of an elastomeric material. The walls of the sleeve portion of the plug are relatively thin, and so the sleeve can stretch slightly to conform snugly to the exterior of the socket barrel as the plug and socket are mated together. It has been found, however, that despite the use of a gasket as described above and despite the snug fit between of the plug sleeve with the exterior of the socket barrel, moisture can enter into the cavity between the mated barrel and sleeve over time during use of the connection formed by the socket and the plug. That moisture can produce corrosion of the mated electrical terminals of the connection, and so cause a fault in one or more of the circuits of which the connection terminals are components. It will be appreciated that, because socket and the plug are mated together at the forward (inside) surface of the tractor wall, it is difficult to obtain access to the plug and to make repairs to it.
Accordingly, there is a need for an improved socket and plug arrangement which makes their connection more secure against the entry of moisture into the cavity between the socket and the plug where their electrical terminals are located. This improvement would also assure that the socket and the plug are correctly mounted to the tractor wall in the first instance.
The present invention provides an electrical plug and socket assembly which seeks to avoid those and other deficiencies and problems found in currently available products. A presently preferred embodiment of the new assembly is described below with reference to the accompanying drawings. The drawings depict the cooperating structures for use in establishing an electrical connection between a tractor and trailer. However, as noted below, a assembly embodying features and principles of this invention can be configured differently for use in other contexts and utilities.
Generally speaking, a socket and plug assembly according to this invention includes an electrical plug comprising a body having an end carrying a plurality of first ones of corresponding pairs of male and female electrical connection moieties. The plug includes a sleeve axially extending from the body end outwardly from the moieties. The sleeve is defined by an outer periphery and an end spaced apart from the body end. Integrally molded with the sleeve is a circumferential flange extending radially from the outer periphery of the sleeve at the sleeve end.
In another aspect of the present invention, the socket and plug assembly comprises a socket comprising a barrel having a first end which is surrounded by a mounting flange and a second end having a plurality of first ones of corresponding pairs of male and female electrical connection moieties. The assembly also includes a plug having a body comprising a plurality of second ones of the corresponding pair of moieties for mating with the plurality of first ones and a plug sleeve axially extending from the body outwardly from the second ones of the connection moieties. The sleeve carries a peripheral flange which has substantially the same outer perimeter shape as that of the socket mounting flange to mate in sealing contact with the mounting flange.